According to Fitter Fitter and Blamey, the petals narrow gradually towards the centre (whereas with Narrow-Fruited Water-cress they get narrow abruptly). Note purple stamens (normally hidden deep within the flower) remaining on one of the growing seed pods (left).

Not to be semantically confused with : Fool's-Water-cress (Apium nodiflorum) [a poisonous plant with similar name which belongs to the Carrot Family (Apiaceae) and which looks like the variety of Water-cress called var. siifolium].

The old genus name (Rorippa) is not to be confused with : the Rorippa genus of Yellow-cresses such as Creeping Yellow-Cress.

An aquatic plant well known as one used as a salad. It is perennial and the leaves are green all year round. Grows in flowing shallow freshwater or on very wet mud and in slow-flowing streams. It is hairless and has hollow stems.

A GLUCOSINOLATE

On of the most widely distributed of all the Glucosinolates in the Cabbage Family (Brassicaceae). Gluconasturtiin, like all glucosinolates, is perfectly harmless to ingest until the plant cells that contain it are damaged, such as occurs when it is chewed in the mouth or attacked by an insect plant pest. It is then that the glucosinolate is acted upon by the enzyme myrosinase (which is also in the cell). The myrosinase detaches the glucose unit from the rest of the molecule to produce an intermediate compound which almost spontaneously rearranges itself from the N-O-HSO3 unit to the isothiocyanategroup -N=C=S which remains bonded to the organic group to become a mustard oil. It is the mustard oil, PhenylEthyl IsoThioCyanate that is toxic, and can also burn the skin.

Gluconasturtiin is also found in Horseradish (Armorcia rusticana) along with another glucosinolate Sinigrin. Both taste bitter in the mouth.